Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933054AbbDJNJw (ORCPT ); Fri, 10 Apr 2015 09:09:52 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:53170 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932434AbbDJNJt (ORCPT ); Fri, 10 Apr 2015 09:09:49 -0400 Message-ID: <5527CB78.4040002@roeck-us.net> Date: Fri, 10 Apr 2015 06:09:12 -0700 From: Guenter Roeck User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Anand Moon , Sjoerd Simons CC: Thierry Reding , Lukasz Majewski , Eduardo Valentin , Russell King , Kukjin Kim , devicetree@vger.kernel.org, "linux-samsung-soc@vger.kernel.org" , linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Markus Reichl Subject: Re: [PATCH 6/6] hwmon: pwm-fan: Update the duty cycle inorder to control the pwm-fan References: <1427387955-5129-1-git-send-email-linux.amoon@gmail.com> <1427387955-5129-7-git-send-email-linux.amoon@gmail.com> <20150408104415.07e1c821@amdc2363> <20150408153214.GA15942@roeck-us.net> <20150408165351.GA22846@roeck-us.net> <1428667201.22057.20.camel@collabora.co.uk> In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-CTCH-PVer: 0000001 X-CTCH-Spam: Unknown X-CTCH-VOD: Unknown X-CTCH-Flags: 0 X-CTCH-RefID: str=0001.0A020202.5527CB9C.020B,ss=1,re=0.001,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0 X-CTCH-Score: 0.001 X-CTCH-ScoreCust: 0.000 X-CTCH-Rules: C_4847, X-CTCH-SenderID: linux@roeck-us.net X-CTCH-SenderID-Flags: 0 X-CTCH-SenderID-TotalMessages: 3 X-CTCH-SenderID-TotalSpam: 0 X-CTCH-SenderID-TotalSuspected: 0 X-CTCH-SenderID-TotalConfirmed: 0 X-CTCH-SenderID-TotalBulk: 0 X-CTCH-SenderID-TotalVirus: 0 X-CTCH-SenderID-TotalRecipients: 0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: mailgid no entry from get_relayhosts_entry X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6896 Lines: 203 On 04/10/2015 05:59 AM, Anand Moon wrote: > Hi Sjoerd, > > I don't much advance knowledge on internal signaling of pwm-samsung module. > > So do I need to send this patch again ? > From the context, it seems that the fix in hwmon would only paint over a problem in the actual pwm driver, correct ? If you resubmit the patch I would expect you to explain this in the commit log. Guenter > -Anand Moon > > > On 10 April 2015 at 17:30, Sjoerd Simons wrote: >> Hey Anand, >> >> On Fri, 2015-04-10 at 16:58 +0530, Anand Moon wrote: >>> Hi Guenter/Lukasz, >>> >>> Earlier I send v2 version of the patch spiking this one. >>> >>> Markus Riechl came back to me with below mail. >>> So This patch confirms fixes the bug. >>> >>> I will send v3 version of the patch. Earlier I was in delima about the bug. >>> >>> -Anand Moon >>> ------------------------------------------- >>> Hi Anand, >>> >>> I tested your patch. >>> >>> After booting the fan is spinning despite only 44?C. >>> >>> /sys/class/thermal/cooling_device0/curstate is 0. >>> /sys/class/hwmon/hwmon4/pwm1 is 0 >>> >>> when I echo 1 > cur_state and then echo 0 > cur_state again, >>> the fan switches to off and behaves as expected. >>> >>> It looks like there is a bug in initializing the pwm output >>> immediately after booting. >> >> The problem here will be that at boot the PWM runs at full duty. With >> the current exynos PWM drive if you disable the PWM it will stop pulsing >> but remain high if it was at 100% duty. My patch on which you depend >> upon fixed a race where disabling the pwm right after changing the duty >> cycle (e.g. to 0%) also kept the signal high. >> >> From looking at other PWM users at the time it seemed that most if not >> all always first set to duty to 0% and then disable the pwm. Which >> should work fine on exynos now. However iirc Thierry recently clarified >> that the expected result of pwm_disable is not just that the modulation >> stops but also that the output signal goes low, although that's not very >> explicit in the current pwm documentation.. The exynos PWM driver will >> need another fix tweak to make that true. >> >> >> >>> Best Regards, >> >> >> >>> -- >>> Markus Reichl >>> >>> On 8 April 2015 at 23:19, Anand Moon wrote: >>>> Hi Guenter, >>>> >>>> Sorry my blunder mistake. Sorry for the noise. >>>> >>>> I just tested with spiking this patch and my observation and testing >>>> were wrong we can skip this patch. >>>> >>>> I will send an v2 patch series removing the patch 5 and patch 6. >>>> >>>> With correct dts changes. >>>> >>>> Thanks for pointing my mistake. >>>> >>>> -Anand Moon >>>> >>>> On 8 April 2015 at 22:23, Guenter Roeck wrote: >>>>> On Wed, Apr 08, 2015 at 09:32:05PM +0530, Anand Moon wrote: >>>>>> Hi Guenter, >>>>>> >>>>>> Initially the board bootup the cooling level state is 0. >>>>>> So update the duty cycle and this power off the fan. >>>>>> As their is no state change the fan will not spin. >>>>>> >>>>>> Once the temperature sensor is reached to alert temperature it changes state. >>>>>> With the state change the fan cools the CPU and then stop's >>>>>> >>>>>> I have observed this state change with tmon utility in linux/tools/thermal/tmon/ >>>>>> >>>>> Sorry, I am missing something. I still don't see what problem you are fixing >>>>> with this patch. What behavior is wrong with the current code, and how does your >>>>> patch fix it ? >>>>> >>>>> Guenter >>>>> >>>>>> -Anand Moon >>>>>> >>>>>> On 8 April 2015 at 21:02, Guenter Roeck wrote: >>>>>>> On Wed, Apr 08, 2015 at 10:44:15AM +0200, Lukasz Majewski wrote: >>>>>>>> Hi Anand, >>>>>>>> >>>>>>>>> Below changes depend on following patch. >>>>>>>>> https://patchwork.kernel.org/patch/5944061/ >>>>>>>>> >>>>>>>>> Update the pwm_config with duty then update the pwm_disable >>>>>>>>> to poweroff the cpu fan. >>>>>>>>> >>>>>>> >>>>>>> Unfortunately, the patch does not include an explanation why it is needed. >>>>>>> >>>>>>> The original code presumably did not update the duty cycle because >>>>>>> pwm was about to be disabled anyway. That kind of made sense to me. >>>>>>> Updating the duty cycle to 0 just to disable the pwm channel right >>>>>>> afterwards does not immediately make sense. >>>>>>> >>>>>>> Given that, I would expect to see a rationale here. Why is this patch needed ? >>>>>>> Does it fix a bug ? If yes, pelase describe the bug. If not, what is the >>>>>>> purpose of this patch ? >>>>>>> >>>>>>> Maybe that is all explained in patch 0/6, which I was not copied on. Even >>>>>>> if so, the reationale will be needed in the changelog to explain to future >>>>>>> developers why this change was made. >>>>>>> >>>>>>> Thanks, >>>>>>> Guenter >>>>>>> >>>>>>>>> Tested on OdroidXU3 board. >>>>>>>>> >>>>>>>>> Signed-off-by: Anand Moon >>>>>>>>> --- >>>>>>>>> drivers/hwmon/pwm-fan.c | 10 ++++------ >>>>>>>>> 1 file changed, 4 insertions(+), 6 deletions(-) >>>>>>>>> >>>>>>>>> diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c >>>>>>>>> index 7c83dc4..f25c841 100644 >>>>>>>>> --- a/drivers/hwmon/pwm-fan.c >>>>>>>>> +++ b/drivers/hwmon/pwm-fan.c >>>>>>>>> @@ -44,26 +44,24 @@ static int __set_pwm(struct pwm_fan_ctx *ctx, >>>>>>>>> unsigned long pwm) int ret = 0; >>>>>>>>> >>>>>>>>> mutex_lock(&ctx->lock); >>>>>>>>> + >>>>>>> >>>>>>> [ please refrain from unnecessary whitespace changes ] >>>>>>> >>>>>>>>> if (ctx->pwm_value == pwm) >>>>>>>>> goto exit_set_pwm_err; >>>>>>>>> >>>>>>>>> - if (pwm == 0) { >>>>>>>>> - pwm_disable(ctx->pwm); >>>>>>>>> - goto exit_set_pwm; >>>>>>>>> - } >>>>>>>>> - >>>>>>>>> duty = DIV_ROUND_UP(pwm * (ctx->pwm->period - 1), MAX_PWM); >>>>>>>>> ret = pwm_config(ctx->pwm, duty, ctx->pwm->period); >>>>>>>>> if (ret) >>>>>>>>> goto exit_set_pwm_err; >>>>>>>>> >>>>>>>>> + if (pwm == 0) >>>>>>>>> + pwm_disable(ctx->pwm); >>>>>>>>> + >>>>>>>>> if (ctx->pwm_value == 0) { >>>>>>>>> ret = pwm_enable(ctx->pwm); >>>>>>>>> if (ret) >>>>>>>>> goto exit_set_pwm_err; >>>>>>>>> } >>>>>>>>> >>>>>>>>> -exit_set_pwm: >>>>>>>>> ctx->pwm_value = pwm; >>>>>>>>> exit_set_pwm_err: >>>>>>>>> mutex_unlock(&ctx->lock); >>>>>>>> >>>>>>>> Reviewed-by: Lukasz Majewski >>>>>>>> >>>>>>>> BTW: I've added Guenter to CC. >>>>>>>> >>>>>>>> -- >>>>>>>> Best regards, >>>>>>>> >>>>>>>> Lukasz Majewski >>>>>>>> >>>>>>>> Samsung R&D Institute Poland (SRPOL) | Linux Platform Group >> >> > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/